Abstract

Hip fractures in older persons are associated with both low levels of daily physical activity and loss of outdoor mobility. The aim of this study was to investigate if accelerometer-based measures of physical behaviour can be used to determine if people undertake outdoor walking and to provide reference values for physical behaviour outcomes related to outdoor mobility in this population. Older persons (n=245) aged ≥70 years one year after hip fracture participated. Six objective outcome measures of physical behaviour collected by a thigh-mounted activity monitor were compared with self-reported outdoor mobility assessed with the Nottingham Extended ADL scale. All measures of time and length in upright (standing and walking) were significantly lower in participants who reported not to walk outdoors (p<0.001). A set of cut-off points for the different physical behaviour variables was generated. Maximum length of upright events discriminated best between groups, with 31 minutes as a threshold to determine if a person is more likely to report that they walk outdoors (sensitivity: 0.805, specificity: 0.704, AUC: 0.871), or 41 minutes or more to determine if a person is more likely to report outdoor walk on their own (sensitivity: 0.802, specificity: 0.833, AUC: 0.891). Physical behaviour variables from activity monitoring can provide information about patterns of physical behaviour related to outdoor activity performance.